Carthage fix

Fix

Fix the Carthage build framework Module Name on macOS && tvOS. The name should now be just SDWebImagePhotosPlugin without any suffix.

Carthage support

Feature

Add fully Carthage support for both iOS 8+ / tvOS 10+ / macOS 10.13+

Docs

Update some comments for documentation

Test

Add test cases for Photos Loader, ensure normal loading / animated image / iCloud loading works

Initial Realse

Support Photos Library loading for SDWebImage 5.0.0-beta